Driveshaft length adjusting devices, especially driveshafts with universal joints in the driveline of or for driving agricultural implements, have at least two tube shaped profiles inserted into one another. An outer profile and an inner profile are axially movable relative to one another along their longitudinal axis and serve to transmit torque. The walls of the outer profile and inner profile, if viewed in cross-section, are partly designed as circular portions. Each wall includes at least one projection which extends parallel to the longitudinal axis. The projection of the inner profile is formed in the form of a drawn-in portion directed inwardly towards the longitudinal axis. The projection of the outer profile forms a wedge and the projection of the inner profile forms a groove which permits engagement of the wedge. The flanks of the wedge and the groove are inclined in such a way that their imaginary extensions intersect a central plane. The plane extends centrally between the flanks and contains the longitudinal axis. A central axis, formed at the intersection of the imaginary planes, is offset from, and parallel to the longitudinal axis towards the respective projection.
A length adjusting mechanism is disclosed in U.S. Pat. No. 4,622,022. Here, the mechanism includes inwardly directed projections each provided with two tapered flanks whose taper points are directed towards one another. Two such projections are provided per profiled tube. As a result of the shape of the projections, a linear contact occurs between the projections of the inner profile and those of the outer profile. This results in an increase in area pressure and a correspondingly high degree of wear.